Wound systems are well known from the prior art and are described, for example, in WO-A2-2005/070807 and WO-A2-2005/070808. Each door is generally formed from a stainless steel sheet or interconnected vertical rigid panels, typically manufactured from metal.
In operation, as the elevator door is opened and closed, the plurality of panels or sheet is wound onto and unwound from a vertical axis in the form of a motorized reel whereby the driving force from the motor is transmitted through the reel and laterally onto the door to provide lateral movement thereof. Normally, the door is biased to its closed position by a weight or spring attached to the leading edge of the door. Accordingly, to open the door, the motor must develop a force which to overcome both the inherent friction and also the counteracting biasing force of the weight or spring to provide the necessary opening acceleration. The biasing force exerted through the door not only biases the door to its closed position but also ensures that the door is tightly wound upon the vertical axis as the door is opened. Both the driving force and the biasing force are laterally transmitted though the door and accordingly the door must be sufficiently strong so as to withstand these lateral forces during operation.
Furthermore, to close the door, the closing force developed by the motor must not be greater than the biasing force. Otherwise the door will unwind from the vertical axis at a pace greater than it is drawn across the opening by the biasing force, which will cause the door to bunch up and will cause the door to jam. Thus, the closing speed of the door is effectively limited by the biasing force.
An objective of the present invention is to provide a door construction with lateral forces transmitted through the door while ensuring that, in operation, the door is tightly wound upon the vertical axis.